Filling an xfa form programmatically

Hello,

    I'm trying to programmatically fill existing signed xfa forms with information from a database. I'm using a library called pdfbox. It works great, except that the <form> tag of the xfa form needs a checksum if modified. I cannot find how to calculate that checksum anywhere. Does Adobe have any product that would let me programmatically fill an xfa form, and modify the contents of the <form> tag?

Thanks,

     Martín.